Perhaps the biggest applause lines came when he reminded the crowd that he worked for eight years as President Obama’s trusted lieutenant.

Joe Biden and wife Jill Biden speak during the kick off former US vice president Biden's presidential election campaign in Philadelphia. (DOMINICK REUTER/AFP/Getty Images)

Biden, who grew up in Scranton and represented Delaware in the Senate, lashed out at Trump for taking credit for the strong economy, asserting that Trump is little more that an entitled, rich, trust-fund kid.

Along with the anti-Trump red meat, Biden portrayed himself as a pragmatic leader who could get things done in Washington. He touted his victory with Obama in passing the Affordable Care Act and the stimulus package that lifted the nation out of the financial crisis.

Biden has taken a strong early lead in polls. Many Democrats see him as the strongest candidate to take on Trump, especially with his proven ability to win a coalition of working-class white voters, liberals and African Americans.

But Biden is fending off questions about the enthusiasm that he inspires among voters. That issue was not put to rest by the launch, which drew a modest crowd on a picture-perfect spring day. Television shots showed garbage trucks and empty streets behind Biden in downtown Philadelphia and a crowd with space to spare.